Charging devices with rotary chutes are inter alia used in shaft furnaces (such as e.g. modern blast furnaces) for providing a more or less uniform distribution of bulk material onto a charging surface inside the furnace. The chute defines for the charging material a chute channel with a concavely curved sliding surface. It is suspended in a cantilever manner from a rotor having a substantially vertical axis of rotation and can be pivoted on this rotor about a substantially horizontal suspension axis to change the inclination of the chute channel. By rotating the rotor about its vertical axis of rotation and simultaneously varying the inclination of the chute by means of a rotating pivoting mechanism, it is consequently possible to distribute the bulk material along a substantially spiral path onto a charging surface in the furnace.
Charging devices with rotary-pivoting chutes are for example described in WO 95/21272, U.S. Pat. No. 5,022,806, U.S. Pat. No. 4,941,792, U.S. Pat. No. 4,368,813, U.S. Pat. No. 3,814,403 and U.S. Pat. No. 3,766,868. In these prior art devices, the rotating pivoting mechanism comprises an auxiliary rotor, which has an axis of rotation substantially coaxial with the main rotor supporting the chute. While the main rotor rotates the chute about a vertical axis, the auxiliary rotor interacts with the rotating chute so as to pivot it about a horizontal suspension axis, thereby varying the inclination of the chute. For this purpose, the auxiliary rotor is connected to the chute by a mechanism converting e.g. a variation in angular displacement between the two rotors into a variation in the angle of inclination of the chute.
It will be appreciated that in prior art charging devices with rotary-pivoting chutes, the pivoting mechanism, used to vary the inclination of the chute channel has to transmit important pivoting moments onto the rotary chute. Indeed, the chute may have a cantilever length several meters, and due to heavy wear and heat protection, it is generally a very heavy construction. It follows that the pivoting mechanism of the rotary chute must be conceived to transmit important pivoting moments onto the rotating chute, which creates a lot of technical problems and makes the charging device rather expensive.
SU-954422 A discloses a charging device with a rotor rotated about a vertical axis of rotation and a chute supported by the rotor. This chute consists of half of a hollow cylinder with a support journal at its top end that is coaxial to the axis of the cylinder. This support journal is connected to an oscillation mechanism on rotor, so that the latter is capable of oscillating the chute about the axis of the cylinder. The bottom end of the chute is cut along a helical line, with half of the pitch equal to 35-50% of the furnace top diameter, leaving a pointed edge end. It will be noted that the chute disclosed in this document is a very cumbersome device that is not really suited for distributing bulk material along a substantially spiral path onto a surface.
SU-954422 A discloses a charging device with a rotor rotated about a vertical axis of rotation and a chute supported by the rotor. This chute consists of half of a hollow cylinder with a support journal at its top end that is coaxial to the axis of the cylinder. This support journal is connected to an oscillation mechanicanism on rotor, so that the latter is capable of oscillating the chute about the axis of the cylinder. The bottom end of the chute is cut along a helical line, with half of the pitch equal to 35-50% of the furnace top diameter, leaving a pointed edge end. It will be noted that the chute disclosed in this document is a very cumbersome device that is not really suited for distributing bulk material along a substantially spiral path onto a surface.